Site-to-Site Tunnel failing...

[FernandoDM]

Hello, Having issues keeping a VPN Site-to-Site tunnel up..

My devices are a FG100D and the remote device is a FG30, both have been updated to v5.2.3 firmware. I set up the site-to-site with the VPN wizard, the VPN tunnel was working for about 3 days and then it stopped.

Tried debugging on the near end (Remote end FG30 device is about an hour drive away, I would like to resolve it from this end if possible without having to drive there). In the debug it says: P1_RETRANSMIT about 3 times then goes to a negotiation timeout, deleting... Connection expiring due to phase1 down.

Tried setting the VPN interface to IKE V1 and aggressive mode but same result. Set it back to IKE2. Not sure if that is the default because setting up with the wizard does not specify. I figured it would default to IKE V2.

Looked at a few forum threads and this one had some interesting commands to restart the VPN tunnel:

https://forum.fortinet.com/tm.aspx?m=107918

# execute router restart

# diagnose debug application ike 2 # diagnose debug enable # diagnose vpn ike restart

Any help is appreciated, Thanks!

[emnoc · Accepted solution]

Logs, show outputs, & configuration details would be nice, also did you do this in  Route or Policy based, but what I would do. if either party are behind  NAT translation; " than enabled nat-T or deploy ikev2 "

2nd config the exact proposals. In fact I would copy the config from  one  FIREWALL and used it at the other side ( just change the interface and address )

for the last step, I would copy the one side  phase2 settings and once again swap the src/dst-subnets details

lastly, ensure that fwpolicy and a route-exists (  the latter is only for route-base )

next, google socpuppet vpn troubleshooting for good t-shoot steps.

socpuppet.blogspot.com/.../site-2-site-routed-vpn-trouble-shooting.html

[Kess]

No way...

Tried some other configurations, also tried to switch to classic tunnel style, tried to rebuild the tunnel from scratch on both ends, but after 2-5 days the only way to resolve the issue is to restart the 60D. Restart of the VM00 has absolutely no effect.

At that point the only thing I can think about is that Fortinet should watch into that.

[Kess]

Hey guys, did someone find a solution for that issue ?

[ede_pfau]

One possible explanation is that when the tunnel goes down traffic is routed out the WAN interface while the tunnel is set up. This session setup is cached so that subsequent traffic follows the default route to the WAN port and not to the tunnel interface.

If there is no traffic to the remote side for a while the session times out and - with the tunnel being up - the next packet traverses the correct route to the tunnel.

This can be easily prevented, as re-iterated in this thread (https://forum.fortinet.com/tm.aspx?m=124305) which refers to an earlier thread. I have supplied a batch command file which defines blackhole routes for all RFC 1912 networks.

If you suspect that this could be the cause, just give it a try. The blackhole routes do not cause harm by themselves.

[Kess]

Hi @ede_pfau

thank you for your reply.

I've read your thread in the past, but unfortunately this isn't the solution of my case.

The IPSec tunnel remains in state "Down" even when forcing it to come up again. The only way to re-establish the tunnel is to reboot the 60D device.

Thx anyway :)

Bye Kess.

[stukat]

I am having a similar issue.  My tunnel 60D to 100D drops several times a day but comes back up.  Problem is that my IP phones are over the tunnel.  Also, I had to rollback to DH5.  DH14 worked but phones wouldn't DHCP. DH20 & 21 never worked; tunnel wouldn't come up.  DH5 is below minimum acceptable standards (and it's still dropping constantly anyway). WOndering if it's an issue with the 60D as I've never had a problem with any of my 100D's. 5.2.2GA on all devices.

[Holy]

Hello Guys,

having the similar problems with 2x 60D. every 1 - 3 days the Tunnels goes down, the same logs and only a Reboot can bring the Tunnels again.

our wan1 is an pppoe and we found yesterday that for that provider we need an mtu size of 1456, we changed the Value and are now hopping that it will save the day.

Fortinet Support don´t know either whats going on. Tunnels are up, IKE MEssages are flowing but there is no response..

i will report if mtu Size will fix the issue.

[TJNIHAL]

Hello Guys,

I am facing the same problem with my 60D tunnel goes down frequently only restart make it up.

I will be very appreciated if you guys let me know how did you resolve this issue.

my current firmware version is V.5.2.6, build 711

Thanks in advance,

Nihal

  

[ksm]

Hi Guys,

We have similar issues in our society. Us, with a 60D behind an ORANGE VDSL2 Line, we regurlarly lose our VPN connection to our DC, average once per week. Only way to retrive it, reboot the modem.

And on a customer with one 60D on its Headquarter. Since he has a Livebox V3 with the Fiber, All its 3 VPN tunnels are down, average once per week.

I have made a lot of tests and debugging, the symptom ( if it is one ) in debug log is always the same phase : P1_RETRANSMIT

Actually I have prepared a 60C to replace our 60D to see if we will have a better behavior, because I do not have 90D for now to test. I will keep you informed.

But if you have a clue, I will take it too !

Support KSM

[ksm]

I would like to add that rebooting the FORTIGATE does not fix the issue, only the modem.

I will try the MTU thing.

Best regards.

Support KSM

[ksm]

Hi,

just to close this post. We decided this morning to stop using the ORANGE Line for mounting VPN connection.

We changed our fortigate for a 90D 2/3 Weeks ago and this morning, loss of the VPN connection, impossible to remount, even after rebooting Fortigate and modem. Last week the VPN has stopped, like about every 7 days, but a couple of minutes after, it was up alone.

After changing the Interface for our other line on Phase 1 both side of VPN tunnel, in a instant, the tunnel was up.

So ***** ORANGE Line.

JS